Patent GB-1036467-A (GB)
Title: Electronic automatic call transmitter, for example for use with automatic telephone systems
IPC: H04M1/27495
Filed: 1963-05-21
Abstract: 1,036,467. Automatic exchange systems. C. F. SCHEEL. May 21, 1963 [May 22, 1962], No. 20168/63. Heading H4K. An electronic impulse sender comprises a pulse source, a pulse counter and a digit counter, the digit counter being arranged to open a gate between the pulse source and the pulse counter for successive counting out of digits set in the pulse counter by means of a number setting device. As shown, Fig. 9, the number setting device comprises switch bank 901 with contact groups 902-907 each of which determines a digit of the required number using a binary code. When the switch is closed contacts 908 close and connect terminals 837, 838 (Fig. 8) applying power to the circuits and producing a pulse at 842 to reset the device. The telephone line La, Lb is looped by transistor switch 862 via battery 863. Audio frequency signals on the line are passed by transformer 870 and amplifier 871 to loud-speaker 872 and integrating amplifier 873 which responds to dial tone, and via AND gate 874 operates bi-stable multivibrator 875 which applies a pulse to digit counter 822. Six AND gates are connected to the bi-stable multivibrators which constitute counter 822 so that pulses are selectively produced at the outputs 831-836 at each count. In response to the pulse from multivibrator 875 a pulse is produced at output 831 and is applied to contact group 902 of the number setting device. Outputs corresponding to the binary 16-complement of the first digit are produced at 911-914 and applied to the set terminals of the bi-stable stages 815-818 of pulse counter 810. Simultaneously an output is produced by OR gate 841 to open AND gate 803 to allow pulses generated by a stable multivibrator 801 to pass to AND gate 805. The output of gate 805 is applied to transistor amplifier 861 which operates line switch 862 to produce dialling pulses on the line La, Lb. The pulses from gate 805 are also applied to the input of counter 810 which counts to 16 and applies a pulse to monostable multivibrator 821 to close 803 for a suitable interdigital period. Simultaneously a pulse is applied by counter 810 to digit counter 822 which routes a pulse to contact group 903 to set up the next digit in counter 810. This is repeated for each of the digits and at the end of the last digit counter 822 is in a state such that OR gate 841 closes AND gate 803 to prevent further transmission of pulses. A monostable multivibrator 876 is started from the reset line and after a suitable delay closes gate 805 to release the loop. If dial tone is received before the end of the delay the delay is restarted. When the required number has been dialled ringing tone or busy tone may be received and heard over loud-speaker 872 and the handset of the regular telephone is lifted to take over the loop and hold the connection before delay device 876 releases the loop. A busy repeat device is illustrated in Fig. 11 which detects busy tone by rectifying the pulses, differentiating them and applying them to an integrating amplifier 1114. This releases the loop and after a delay determined by monostable multivibrator 1117 resets the counters, loops the line and redials the number. The number of times the transmission is repeated is determined by the number of stages in a counter 1116. The power supply comprises a rechargeable battery 863 recharged by the line current, rectifier bridge 865 being incorporated to secure polarity independence of the line connection. The switch bank 901 determines a single number and a plurality of these banks may be parallelled at 909. Alternatively bank 901 may be replaced by permanent connections and a sevenpole switch, shown as a cross at 910, several banks of this type being paralleled at 919. In a PABX the transmitter can be arranged to dial the number required to obtain an outside line before dialling the wanted subscriber's number as described above. The device may also be used to automatically set up connections between electronic data machines or to operate as a fire or burglar alarm or to give warning of faults in unattended plant by automatically calling a predetermined telephone number.